1. Field of the Invention
The present invention relates to an image forming device and a developing cartridge mounted on the image forming device.
2. Related Art
There has been provided an image forming device, such as a laser beam printer. A developing cartridge is mounted on the conventional laser beam printer. The developing cartridge includes a toner chamber, an agitator, a developing roller, a regulation blade, and a photosensitive drum.
The toner chamber houses a non-magnetic single component toner. The agitator is provided within the toner chamber for agitating the toner and for supplying the toner onto the developing roller. The toner supplied to .the developing roller is held on its peripheral surface and forms a toner layer thereon. The regulation blade regulates the thickness of the toner layer, and also charges the toner by friction.
The photosensitive drum is provided in confrontation with the developing roller, and an electrostatic latent image is formed thereon. When the rotation of the developing roller transports the toner layer to the photosensitive drum, charged toner is selectively transferred from the developing roller onto the photosensitive drum, thereby developing a visible toner image corresponding to the electrostatic latent image on the photosensitive drum.
In this type of laser beam printer, a photosensor is provided for detecting the amount of the toner remaining in the toner chamber. The photosensor includes a light emitting element and a light receiving element provided each side of the toner chamber so as to interpose the toner chamber therebetween. The toner chamber is formed with light transmission windows through which a light emitted from the light emitting element reaches the light receiving element.
The agitator rotates and lifts up the toner for agitation at a predetermined frequency. Therefore, the lifted-up toner temporarily blocks the light from reaching the light receiving element at the predetermined frequency. Both the time duration for letting the light to transmit to and reach the light receiving element and the time duration for blocking the light from reaching the light receiving element depend on the amount of the remaining toner. Accordingly, by detecting the time duration of the light transmission, the reaming amount of the toner can be detected.
The laser beam printer is usually provided with a motor serving as a driving power source. The driving power of the motor is transmitted to both the developing roller and the agitator via a transmission gear mechanism, thereby driving the developing roller and the agitator to rotate.
There has been also provided a laser beam printer capable of printing at a high speed rate. In order to increase the printing speed, it is required to rotate the agitator and the developing roller at higher speed. High-speed rotation of the agitator efficiently agitates or circulates the toner within the toner chamber, and so an increased amount of toner, which is efficiently charged, is supplied to the developing roller. Also, high-speed rotation of the developing roller efficiently develops visible toner images corresponding to electrostatic latent images on the photosensitive drum.
However, high-speed rotation of the agitator stirs up the toner, and fills the toner chamber with clouds of toner. This cloud of toner blocks the light of the photosensor from reaching the light receiving element, regardless of the remaining toner amount, thereby preventing accurate detection of remaining toner amount.
In order to overcome the above problems, it is conceivable to rotate the agitator at higher speed during printing and at lower speed during toner amount detection. However, because the agitator is driven by a driving mechanism that also drives the developing roller, when the rotation speed of the agitator is slowed down, the rotation speed of the developing roller is also slowed down. The change in rotation speed of the developing roller changes the developing condition, resulting in undesirable printed image, such as, redundancy in printing.
It is an objective of the present invention to overcome the above problems and also to provide an image forming device and a developing cartridge used in the image forming device capable of detecting an accurate amount of remaining toner and forming high quality image at high speed.
In order to achieve the above and other objectives, there is provided a developing cartridge used in an image forming device. The developing cartridge includes a chamber that is rotatable and houses a developing agent, a holding member that holds the developing agent, an agitator that is rotatably provided within the chamber, and agitates the developing agent, and supplies the developing agent to the holding member, The holding member and the agitator rotate independent from each other.
There is also provided an image forming device, including a chamber that houses a developing agent, a holding member that holds the developing agent, an agitator that is provided within the chamber and agitates the developing agent, an agitator driving mechanism that drives the agitator to rotate at different speed. The holding member and the agitator rotate independent from each other.
Further, there is provided an image forming device including a chamber that houses a developing agent, a holding member that rotates and holds the developing agent, an agitator that rotates within the chamber to agitate the developing agent, a sensor that detects an amount of the developing agent remaining in the chamber, and an image forming mechanism that performs an image forming operation. The agitator rotates independent from the holding member. The agitator rotates at a lower speed when the sensor detecting the amount of the developing agent than when the sensor is undetecting the amount of the developing agent.
There is also provided a developing cartridge used in an image forming device, including a chamber that houses a developing agent, a holding member that is rotatable and holds the developing agent, an agitator that is rotatable provided within the chamber, agitates the developing agent, and supplies the developing agent to the holding member, and windows formed to the chamber. The windows defines a light transmitting path. The holding member and the agitator rotate independent from each other.